Hi everybody, a newbie question:
for the raster in GRASS, is it possible to have for each pixel several attributs or is it limited to one attribut (cat) per pixel ?
Thanks
Mick
Michaël Rabotin wrote:
Hi everybody, a newbie question:
for the raster in GRASS, is it possible to have for each pixel several
attributs or is it limited to one attribut (cat) per pixel ?
Each cell has a single value (category), which can be associated with
a single attribute.
However, you can create "reclass" maps which share the same underlying
raster data but with the categories remapped (you can use an identity
mapping if you only want to change the categories' attributes).
Reclass maps are essentially "views" of an existing map.
A reclass map can have its own category attributes, colour table, etc.
Reclass maps typically require significantly less storage than normal
raster maps. If you replace the base map, any reclass maps which are
based upon will be updated automatically (a reclass map just consists
of the name of the base map and a list of category mappings).
E.g. in the Spearfish sample data set, the soil.br.depth,
soils.Tfactor, soils.ph, soils.range and texture maps are all reclass
maps based upon the soils map.
--
Glynn Clements <glynn@gclements.plus.com>
Michaël Rabotin wrote:
for the raster in GRASS, is it possible to have for each pixel several
attributs or is it limited to one attribut (cat) per pixel ?
not specifically, but a CELL (integer) map could use the 2^n trick:
cell value is comination of 1+2+4+8+16+32+...
feature A is "1"
feature B is "2"
feature C is "4"
feature D is "8"
etc...
so if pixel has features A,C,D but not B, the cell value = 13.
???
In general the raster is a grid of actual data, not a grid of points.
I guess if raster contains less than 1 million cells you could do
"r.to.vect feature=point", then link many attributes to each point in a
DB table.
Hamish